Traditional medical and surgical treatment of patients with failing pump function of the heart is limited to blood-contacting devices which are technically difficult to install and result in complications related to such blood contact as well as technical aspects of device installation. Inadequate cardiac output remains a cause of millions of deaths annually in the United States. Mechanical devices are proving to be a practical therapy for some forms of sub-acute and chronic low cardiac output. However, all currently available devices require too much time to implant to be of value in acute resuscitation situations, resulting in loss of life before adequate circulatory support can be provided. Furthermore, other non-blood contacting devices similar to the current invention provide inadequate augmentation of cardiac function. Mechanical cardiac assistance devices generally operate by providing blood pumping support to the circulation to assist the failing heart.
A number of mechanical techniques for assisting heart function by compressing its outer epicardial surface have been described and studied. These methods have focused on improving cardiac performance by assisting the systolic (positive pumping) function of the heart. Such techniques have been described as “direct cardiac compression” (DCC). DCC methods have been investigated only in the laboratory setting, and there are no uses of such devices in human subjects known to the applicants. Investigations regarding DCC have focused primarily on left ventricular (LV) systolic and diastolic performance. Examples of DCC techniques include, but are not limited to, cardiomyoplasty (the technique of wrapping skeletal muscle around the heart and artificially stimulating it), the Cardio support system (Cardio Technologies, Inc., Pinebrook, N.J.) and the “Heart Booster” (Abiomed, Inc., Danvers, Mass.). Cumulative results from laboratory investigations using these devices have all resulted in similar findings. Specifically, DCC has been shown to enhance left ventricular (LV) pump function without any apparent change in native LV oxygen consumption requirements; thereby, DCC has been shown to improve LV pump function without increasing myocardial oxygen consumption and/or requiring extra work from the heart.
DCC devices have been shown to only benefit hearts with substantial degrees of LV failure. Specifically, DCC techniques only substantially improve the systolic function of hearts in moderate to severe heart failure. In addition, the benefits of DCC techniques are greater when applied to the relatively dilated or enlarged LV. Therefore the relative degree of assistance provided by DCC improves as heart failure worsens and the heart enlarges or dilates from such failure. DCC techniques clearly have a negative effect on diastolic function (both RV and LV diastolic function). This is exhibited by reductions in diastolic volume that, in part, explains DCC's inability to effectively augment the heart without at least moderate degrees of failure. This also explains DCC's efficacy being limited to sufficient degrees of LV size and/or dilatation, with significant dependence on preload, and/or ventricular filling pressures. Thus, DCC requires an “adequate” degree of heart disease and/or heart failure to benefit the heart's function. In addition, DCC devices have negative effects on the dynamics of diastolic relaxation and, in effect, reduce the rate of diastolic pressure decay (negative dP/dt max), increasing the time required for ventricular relaxation. This better explains why DCC techniques require substantial degrees of LV and RV loading (i.e. increased left and right atrial pressure or “preload”) to be effective, as such increases serve to augment ventricular filling. This latter point is particularly true with smaller heart size and/or less ventricular distension.
The critical drawbacks to DCC methods are multi-factorial and are, in part, summarized in the following discussion. First, and foremost, these techniques do not provide any means to augment diastolic function of the heart necessary to overcome their inherent drawback of “effectively” increasing ventricular stiffness. This is illustrated by the leftward shifts in the end-diastolic pressure-volume relationship (EDPVR) during DCC application. This effect on the EDPVR is seen with DCC devices in either the assist or non-assist mode. Clearly, RV diastolic function is impaired to a far greater degree by DCC due to the nature both the RV wall and intra-cavity pressures. Furthermore, studies of DCC devices have all overlooked the relevant and dependent impact these techniques have on right ventricular dynamics, septal motion and overall cardiac_function. Because the right ventricle is responsible for providing the “priming” blood flow to the left ventricle, compromising right ventricular function has a necessary secondary and negative impact on left ventricular pumping function when these load-dependent devices are utilized. Furthermore, the ventricular septum lies between the right and left ventricle and is directly affected by the relevant forces placed on both the RV and LV. Another related and fundamental drawback to DCC devices is their inability to continuously monitor ventricular wall motion and chamber dynamics that are intuitively critical to optimizing the assist provided by such mechanical actions on the right and left ventricular chambers which behave in an complex, inter-related fashion. Finally, studies regarding DCC methods have failed to adequately examine the effects of these devices on myocardial integrity.
The Direct Mechanical Ventricular Assist device (hereinafter abbreviated as DMVA) is an example of one type of mechanical cardiac assistance device. In general, a DMVA system comprises two primary elements: (a) a Cup having dynamic characteristics and material construction that keep the device's actuating liner membrane or diaphragm closely conformed to the exterior surface (or epicardium) of the heart throughout systolic and diastolic actuation, and (b) a Drive system and control system combination that cyclically applies hydraulic pressure to a compression and expansion liner membrane or membranes located on the interior surfaces of the Cup in a manner that augments the normal pressure and volume variations of the heart during systolic and diastolic actuation. The cyclic action of the device cyclically pushes and pulls on the left and right ventricles of the heart.
By providing this cyclic motion at the appropriate frequency and amplitude, the weakened, failing, fibrillating, or asystolic heart is driven to pump blood in a manner which approximates blood flow generated by a normally functioning heart. Pushing inwardly on the exterior walls of the heart compresses the left and right ventricles into systolic configuration(s), thereby improving pump function. As a result, blood is expelled from the ventricles into the circulation. Immediately following each systolic actuation, the second phase of the cycle applies negative pressure to the liner membrane to return the ventricular chambers to a diastolic configuration by pulling on the outer walls of the heart. This is termed diastolic actuation and allows the ventricular chambers to refill with blood for the next compression.
In the preferred embodiment of the present invention, the Cup is installed on the heart typically by using apical vacuum assistance, i.e. vacuum applied to the apex of the Cup. Such a preferred embodiment enables a non-traumatic and technically simple means of cardiac attachment of the Cup device in the patient and facilitates diastolic actuation. To install the Cup, the heart is exposed by a chest incision., The Cup is positioned over the apex of the heart in a position such that the apex of the heart is partially inserted therein. A vacuum is applied to the apex of the Cup, thereby pulling the heart and the Cup together, such that the apices of the Cup and the heart, and the inner wall of the Cup and the epicardial surface of the heart become substantially attached. Connections are then completed for any additional sensing or operational devices (typically integrated into a single interface cable) if the particular Cup embodiment comprises such devices. This procedure can be accomplished in minutes, and it is easy to teach to individuals with minimal surgical expertise.
Effective DMVA requires that the Cup and Drive system satisfy multiple and complex performance requirements. Preferred embodiments of the Cup of the present invention satisfy these critical performance requirements in a manner that is superior to prior art DMVA devices.
Heretofore, a number of patents and publications have disclosed Direct Mechanical Ventricular Assist devices and other cardiac assistance devices, the relevant portions of which may be briefly summarized as follows:
U.S. Pat. No. 2,826,193 to Vineberg discloses a Ventricular Assist device that is held to the heart by a flexible draw-string. Vineberg uses a mechanical pump to supply systolic pressure to the heart to assist the heart's pumping action.
U.S. Pat. No. 3,034,501 to Hewson discloses a similar Ventricular Assist device, comprised of silastic, which permits varying pressures to be exerted on various portions of the heart.
U.S. Pat. No. 3,053,249 to Smith discloses a Ventricular Assist device capable of delivering systolic pressure to a heart. The Smith device utilizes adhesive straps to attach the device to the heart.
U.S. Pat. No. 3,233,607 to Bolie illustrates a Direct Assist device that varies the level of systolic pressure depending on the changes of blood flow occasioned by exercise. The Bolie device claims to be fully implantable. U.S. Pat. No. 3,449,767 to Bolie discloses a system for controlling the pressure delivered to the balloons that control the DMVA unit.
U.S. Pat. No. 3,279,464 to Kline teaches a method of manufacture of a Ventricular Assist device. Kline's device provides only systolic pressure to the heart.
U.S. Pat. No. 3,371,662 to Heid discloses a Ventricular Assist device in the form of a cuff. The cuff may be implanted with defibrillating electrodes.
U.S. Pat. No. 3,376,863 to Kolobow illustrates a Ventricular Assist device that delivers systolic pressure to the heart. The Kolobow device possesses an expandable collar about the periphery of the device's opening. The heart may be sealed within the device by expanding the collar.
U.S. Pat. No. 3,455,298 of Anstadt discloses a Direct Mechanical Ventricular Assist device capable of delivering both systolic and diastolic pressures. The diastolic action is achieved by use of a vacuum. A second vacuum source functions to hold the device to the heart. Anstadt further defines the geometry of the device in U.S. Pat. No. 5,199,804. The geometry of the invention is described so as to accommodate hearts of various sizes as well as prevent the heart from being expelled from the device during the systolic expansion of the bladders.
U.S. Pat. No. 3,478,737 of Rassman discloses a Ventricular Assist device in the form of a cuff.
U.S. Pat. No. 3,513,836 to Sausee discloses a Ventricular Assist device that delivers systolic pressure to the heart by a multiplicity of bladders. Increasing the pressure in selected bladders may preferentially pressure selected portions of the heart.
U.S. Pat. No. 3,587,567 to Schiff discloses a Direct Mechanical Ventricular Assist device that is capable of delivering both systolic and diastolic pressures to a heart. The device may further comprise electrodes that permit defibrillation of the heart. The device is held to the heart by a mild vacuum pressure, which also supplies the diastolic action.
U.S. Pat. No. 3,613,672 to Schiff discloses a cup with a flexible outer shell that allows for the insertion of the device through a relatively small surgical incision. The patent also discloses the use of sensors, such as electrocardiogram equipment, in conjunction with the cup. Additional reference may be had to U.S. Pat. Nos. 3,590,815 and 3,674,381 also to Schiff.
U.S. Pat. No. 4,048,990 to Goetz discloses a Ventricular Assist device that delivers both systolic and diastolic pressures to a heart. The outer shell of the Goetz device is inflatable, so as to allow installation with minimal trauma to the patient.
U.S. Pat. No. 4,448,190 to Freeman discloses a Ventricular Assist device that delivers systolic pressure to a heart by means of a strap physically attached to the heart. A similar device is disclosed in U.S. Pat. Nos. 5,383,840 and 5,558,617 to Heilman. The Heilman patent discloses the use of defibrillation devices and materials that promote tissue in-growth to assist in adhering the device to the heart.
U.S. Pat. No. 4,536,893 to Parravicini discloses a Ventricular Assist device in the form of a cuff that applies pressure to selected portions of the heart. The patent also discloses the use of sensors, such as an electrocardiograph, in conjunction with the cuff.
U.S. Pat. No. 4,621,617 to Sharma discloses a Ventricular Assist device wherein the heart is disposed within two sheets of metal. An electromagnetic field draws the sheets together, thus compressing the heart.
U.S. Pat. No. 4,690,134 to Snyders discloses a Ventricular Assist device with a collapsible outer shell. Such a device may be installed with minimal trauma to the patient. Additional reference may be had to U.S. Pat. Nos. 5,169,381 and 5,256,132 also to Snyders.
U.S. Pat. No. 4,979,936 to Stephenson discloses a fully implantable Ventricular Assist device. Stephenson's device comprises a first bladder fluidly connected to a second bladder. The first bladder is disposed within a muscle, while the second bladder is disclosed next to or around the heart. The muscle may then be electrically contracted, thus, forcing fluid out of the first bladder and into the second bladder. The expansion of the second bladder thus compresses the heart.
U.S. Pat. No. 5,273,518 to Lee discloses a fully implantable Ventricular Assist device similar to the muscle powered devices mentioned above. U.S. Pat. Nos. 5,098,442 and 5,496,353 to Grandjean, 5,562,595 to Neisz, 5,658,237, 5,697,884, and 5,697,952 to Francischelli, 5,716,379 to Bourgeois and 5,429,584 to Chiu disclose a similar device. U.S. Pat. No. 5,364,337 to Guiraudon discloses a means for controlling the contraction of the muscle, which in turn, controls the compression of the heart.
U.S. Pat. No. 5,098,369 to Heilman discloses a Ventricular Assist device that is comprised of materials that allow for tissue in-growth, thus adhering the device to the heart. The use of defibrillating electrodes and electrocardiographs are also disclosed.
U.S. Pat. No. 5,131,905 to Grooters discloses a Ventricular Assist device that applies systolic pressure to the heart. The Grooters device is held in position around the heart by a plurality of straps.
U.S. Pat. Nos. 5,385,528, 5,533,958, 5,800,334, and 5,971,911 to Wilk disclose a Direct Mechanical Ventricular Assist device suitable for emergency use. The inflatable device may be quickly installed in an emergency situation through a small incision. U.S. Pat. No. 6,059,750 to Fogarty discloses a similar device.
U.S. Pat. No. 5,713,954 to Rosenberg discloses a Ventricular Assist device in the form of a cuff that provides systolic pressure to a heart. The disclosed cuff is suitable for applying pressure to specified portions of the heart, may be equipped with EKG sensors, and is fully implantable.
U.S. Pat. Nos. 5,738,627 and 5,749,839 to Kovacs disclose a Direct Mechanical Ventricular Assist device that provides both systolic and diastolic pressure to a heart. The disclosed cup adheres to the heart by way of a vacuum, which also provides' diastolic pressure to the heart. The opening of the device is equipped with an inflatable collar. When inflated, the collar provides a seal to assist in establishing the vacuum.
U.S. Pat. No. 6,076,013 to Brennan discloses a cup that senses electrical activity within the heart and provides electrical stimulation to assist the heart in its contractions.
U.S. Pat. No. 6,110,098 to Renirie discloses a method for treatment of fibrillation or arrhythmias through the use of subsonic waves.
U.S. Pat. No. 6,206,820 to Kazi discloses a Ventricular Assist device that compresses only the left ventricle and allows the other cardiac regions to expand in response to the contraction.
U.S. Pat. No. 6,238,334 to Easterbrook discloses a Ventricular Assist device that provides both systolic and diastolic pressure to a heart. Easterbrook discloses the use of a cup to apply a substantially uniform pressure to the heart's surface, which is necessary to avoid bruising of the muscle issue. Through the reduction of transmural pressure, a substantially lower driving pressure may be utilized. This assists to avoid traumatizing heart tissue.
U.S. Pat. No. 6,251,061 to Hastings discloses a Ventricular Assist device that provides systolic pressure to a heart through the use of ferrofluids and magnetic fields.
U.S. Pat. No. 6,432,039 to Wardle discloses a Ventricular Assist device that comprises a multiplicity of independently inflatable chambers that delivery systolic pressure to selected portions of a heart. Wardle also discloses the use of redundant “recoil” inflatable balloons.
U.S. Pat. No. 6,464,655 to Shashinpoor discloses a fully implantable robotic hand for selectively compressing the ventricles of a heart. The robotic hand is programmable via a microprocessor.
U.S. Pat. Nos. 6,328,689 to Gonzalez and 6,485,407 to Alfemess disclose a flexible jacket adapted to be disposed about a lung. By applying expansive and compressive forces, the lung may be assisted.
Optimal DMVA performance requires that the Cup be properly fit on the heart, be adequately sealed against the ventricular epicardium, and that the volume vs. time displacement profile of the Cup liner(s) produces the desired ventricular dynamics to achieve optimal, dynamic systolic and diastolic conformational changes of the ventricular myocardium. The optimum pressure-flow drive mechanics will vary from patient to patient, depending upon such factors as the actual fit of the Cup to the heart, the specific nature of the patient's disease, and the patient's normal cardiac rhythm. These factors make it difficult to pre-operatively define the optimum liner time-displacement profiles or hydraulic drive unit control parameters capable of satisfying every patient's unique DMVA requirements.
It is well known that diseased heart tissue can be very fragile, i.e. such tissue is of lower resistance to shear forces and/or less tensile strength than healthy heart tissue. Thus physicians lacking due caution can easily perforate or injure diseased hearts with their fingers while applying gentle pressure during open heart massage by the high pressure at a finger tip adjacent to a low pressure or pressure void between fingers. This previous example describes an acute or rapidly induced emergency situation. However, the persistent application of forces to the heart can also cause potentially catastrophic damage to the heart by fatiguing and severely bruising the heart muscle and/or abrading the heart surface, which can ultimately prevent the heart from functioning.
Direct mechanical ventricular actuation (DMVA) is a means of providing ventricular actuation to achieve biventricular compression (termed “systolic actuation”) and active biventricular dilatation (termed “diastolic actuation”). In one embodiment, DMVA utilizes continuous suction to maintain a seal between the actuating diaphragm and the surface of the heart, which enables the device not only to compress the heart, but also effectively provide diastolic actuation by virtue of the diaphragm maintaining attachment to the epicardial surface during the phase of ventricular actuation. Therefore, DMVA overcomes major drawbacks of DCC devices by augmenting diastolic function. This is essential, given that any such DCC device that encompass the ventricles and applies external forces will have inherently negative impacts on diastolic function. The present invention overcomes this, by enhancing diastolic function as demonstrated by an increased rate of diastolic pressure decay and an associated reduced time constant for active ventricular chamber dilatation (“diastolic actuation”).
The general principles of effective ventricular compression and ventricular dilatation can only be delivered in an optimal fashion if the effects on both right and left ventricular function are taken into account and such forces are applied in the appropriate temporal and spatial distribution, which is dictated by the material characteristics and delivery of the appropriate drive mechanics using appropriately fashioned pressure and/or flow dynamic profiles. These drive dynamics and material characteristics of the diaphragm and housing of the device are also critical in achieving the best functional result, with the least cardiac trauma.
The appropriate dynamic fit of the DMVA device and its interaction with the heart throughout the actuating cycle is critical, and mandates that RV/LV dynamics are monitored. In particular, fit of the device in the diastolic mode must allow for adequate expansion of both the LV and RV chambers, with particular attention to the RV due to its lower-pressure, compliant properties. Inadequate size and/or diastolic assist will predominantly compromise RV filling, resulting in diminished RV output, and in turn, reductions in overall cardiac output. In contrast, systolic actuation places emphasis on adequate degrees of LV compression. Adequate LV chamber compression requires attention to regulation of variables including maximum systolic drive volume delivery, maximum systolic pressure, and systolic duration.
More simply stated, adequate LV compression is that degree of compression that results in LV stroke volumes approximately equal to optimal RV stroke volumes. The inter-relationship of these chambers dictates that both RV and LV chambers need to be monitored. Appropriate RV and LV actuation by the DMVA system requires active, real-time measurement of both operational parameters and hemodynamic responses, which are utilized in the DMVA adaptive control algorithms to achieve optimal pump function and other more sophisticated operations such as device weaning and analysis of myocardial recovery.
Functional interactions between the right ventricle and left ventricle under mechanical systolic and diastolic actuation are relatively complex and difficult to describe and/or characterize. These are dynamic interactions that are not necessarily predictable based on pre-measured variables, but rather depend on a broad number of physiologic variables. These interactions are not independent; thus the behavior of one chamber has an impact on the other. Continuous monitoring of these two chambers allows the drive control to utilize an adaptive algorithm to constantly alter DMVA control parameters to achieve optimal cardiac actuation and hemodynamic output. Examples of this include, but are not limited to adjustment of pressure/volume relationships to maintain balanced RV/LV output, control of pressure rise times to avoid herniation of the right ventricle, and reduction of negative drive pressure during diastole based on loss of contact between the DMVA liner and the heart wall.
The variability of a broad range of physiologic states across the patient population will dictate that these and other parameters will require responses that may be somewhat unique to each patient. Thus parametric control that benefits from broad demographic information, from physician input, and from real-time patient response data will result in the best outcome for the individual patient.
Therefore a heart-assist device is needed that does not cause damage to the heart as a result of its mechanical action on the heart. There also exists a need for a sensing and control means to ensure that such a device (1) is properly positioned and/or installed on the heart, (2) adequately seals against the heart, (3) achieves the desired systolic and diastolic action at installation and over the implanted life of such device, (4) operates within desired parameters to achieve optimal cardiovascular support, and (5) detects changes, such as impending device failure, in time to take corrective action.
There is also a need for a process to accomplish the above tasks very quickly, in order to avoid brain death and other organ damage. The inherent ability of the DMVA Cup of the present invention to be installed in a very short period of time with no surgical connection to the cardiovascular system of the patient needed enables the Cup of the present invention to save patients who require acute resuscitation, as well as to minimize the number of failed resuscitations due to improper installation or drive mechanics.
There is also a need for a device that does not contact the blood so that anticoagulation countermeasures are not needed, and so that the potential for infection within the blood is reduced.
It is therefore an object of this invention to provide a Direct Mechanical Ventricular Assist device that does not do damage to the heart as a result of its mechanical action on the heart.
It is a further object of this invention to provide a Direct Mechanical Ventricular Assist device that is technically straightforward to properly install on the heart.
It is an additional object of this invention to provide a Direct Mechanical Ventricular Assist device that may be installed on the heart and rendered functional by a procedure that is accomplished in a few minutes.
It is another object of this invention to provide a Direct Mechanical Ventricular Assist device that adequately seals against the heart, thereby enabling more precise operation of the device.
It is an additional object of this invention to provide a Direct Mechanical Ventricular Assist device that drives the systolic and diastolic action of the heart within precisely defined and controlled parameters.
It is a further object of this invention to provide a Direct Mechanical Ventricular Assist device that provides a healing environment within the body of the patient, including the heart itself.
It is another object of this invention to provide a Direct Mechanical Ventricular Assist device that provides measurements of the systolic and diastolic action of the heart to which it is fitted.
It is a further object of this invention to provide a Direct Mechanical Ventricular Assist device that provides an image of the functioning heart to which it is fitted.
It is a further object of this invention to provide a Direct Mechanical Ventricular Assist device that contains sensors and provides sensory feedback relative to the functioning heart to which it is fitted.
It is another object of this invention to provide a Direct Mechanical Ventricular Assist device that can provide electrical signals to the heart to pace the systolic and diastolic functions thereof.
It is an object of this invention to provide a Direct Mechanical Ventricular Assist device that has no direct contact with circulating blood, thereby reducing the risk for thrombogenic and bleeding complications, decreasing the potential for infection of the blood, and eliminating the need for anticoagulation that has many serious complications, especially in patients with serious cardiovascular disease and recent surgery.
It is another object of this invention to provide electrophysiological support, such as pacing and synchronized defibrillation, that can be integrated with mechanical systolic and diastolic actuation.
It is another object of the present invention to provide a DMVA device that can augment cardiac function without any surgical insult to the heart and/or great vessels.
It is another object of the present invention to provide a DMVA device that can put the heart to rest so that it can heal itself from an acute insult while having an improved flow of oxygenated blood.
It is a further object of the present invention to provide a DMVA device having a detachable liner, which can thus enable the DMVA device to be removed from the patient with no trauma to the heart of the patient.
It is a further object of the present invention to provide a DMVA device having a therapeutic liner or seal, thereby enabling the direct administration of therapeutic agents to the heart of the patient.
It is a further object of the present invention to provide a DMVA device that allows dynamic monitoring of the operation thereof, and the resultant right ventricle and left ventricle actuation, to permit optimization of pump function of the heart.
It is a further object of the present invention to provide a DMVA device comprising a volumetrically regulated fluid drive utilizing drive flow/volume sensors integrated with sensing and analysis of DMVA device/biventricular interactions, thereby enabling optimization of resulting biventricular actuation.
It is a further object of the present invention to provide a DMVA device comprising a pressure regulated drive that regulates DMVA drive mechanics independent of volume, utilizing analysis of drive pressure dynamics integrated with analysis of volume changes with the cup and within the right and left ventricles.